Various technologies are being developed to replace the gasoline-powered internal combustion engine. One reason for this is the fact that within the foreseeable future, petroleum reserves will be depleted. Another reason for this is that because ever stricter environmental regulations are putting great pressure on energy companies and automobile manufacturers to develop cleaner burning fuels and cleaner running vehicles. For example, the conventional internal combustion engine produces pollutants such as particulates, nitrogen oxides, sulfur oxides, hydrocarbons and carbon monoxide. While various alternative fuel technologies have been proposed and are the subject of a substantial amount of research and development, the hydrogen powered fuel cell is thought to be ideal alternative to fossil fuel systems. The primary reason for this is because hydrogen, which is derived from all kinds of renewable energies, is the only energy carrier which can be used without any environmental damage. The production of energy from hydroenergy (energy from hydrogen) and solar energy and its conversion into electrical and thermal energy with a fuel cell presents a process cycle, which can be repeated without limits, producing no ecological harmful side products.
The failure to produce a practical storage system for hydrogen has prevented hydrogen from coming to the commercial forefront as a transportation fuel. The ideal hydrogen storage system needs to be light, compact, relatively inexpensive, safe, easy to use, and reusable without the need for regeneration. While research and development is continuing on such technologies as: liquid hydrogen systems, compressed hydrogen systems, metal hydride systems, and super activated carbon systems, all of these systems have serious disadvantages. For example, liquid hydrogen systems are very expensive, primarily because the hydrogen must be cooled to about -252.degree. C. For example, a liquid hydrogen system will cost about four times more than an equivalent mount of gasoline. Further, liquid hydrogen must be kept cold to prevent it from boiling away, even when the vehicle is parked. Compressed hydrogen is much cheaper than liquid hydrogen, but it is much bulkier. Even at 6,000 psig, tanks of compressed hydrogen, which would be capable of supplying enough fuel for a standard family automobile to cover about 350 miles, would take up about 4 to 5 times as much space as a conventional gasoline tank. Also, a tank of compressed hydrogen is not only very dangerous, but it will be excessively heavy and expensive for the average all purpose family vehicle.
Metal hydride systems store hydrogen as a solid in combination with other materials. For example, metal hydrides are produced by bathing a metal, such as palladium or magnesium, in hydrogen. The metal splits the two-atom hydrogen gas molecules and binds the hydrogen atoms to the metal until released by heating. The disadvantages of a metal hydride system are: (i) metal halides typically weigh about 8 times more than an equivalent amount of liquid hydrogen, or an equivalent amount of gasoline; and (ii) they must be heated to relatively high temperatures before they give up hydrogen.
Superactivated carbon is the basis of another system for storing hydrogen which initially showed commercial potential. Super activated carbon is a material similar to the highly porous activated carbon used in water filters, but which can gently hold hydrogen molecules by physisorption at sub-zero temperatures. The colder the carbon, the less heat that is needed to disturb the weak forces holding the carbon and hydrogen together. Again, a major disadvantage of such a system is that in order to prevent the hydrogen from escaping the system must constantly be kept at very low temperatures, even when the vehicle is parked.
Technology is also being developed wherein hydrogen is liberated from the reaction of powdered iron and water. When the driver presses on the gas pedal, a burst of steam sprays over a bed of powdered iron, packed into long tubes. Hydrogen gas immediately forms and is injected into a fuel cell, which will then generate a current for an electric motor. The resulting oxidized iron, or rust, will remain behind. A major disadvantage of such a system is that the system must be heated to several hundred degrees before the hydrogen-producing reaction can occur and the resulting metal oxide must be regenerated or replaced.
Consequently, there still remains a great need in the art for a material which can store hydrogen and which is light, compact, relatively inexpensive, safe, easy to use, and reusable without regeneration.